Animal bites and suspected human rabies exposures

Animal bites are a public health concern because of the potential for transmission of rabies, a viral infection of the nervous system and brain of humans and other mammals that is almost always fatal. A suspected human rabies exposure occurs when saliva or other possibly infectious material (such as central nervous system tissue) from a potentially infected animal penetrates the skin or comes into contact with mucosal surfaces. Rabies is not transmitted by contact with blood, urine, feces, or fur.

Exposure to bats requires special attention because bat variant rabies has been documented in persons with no history of a scratch or a bite. Any potential human exposure to a bat requires careful assessment because bat teeth are razor sharp and tiny, so a bite wound may not be detectable on physical examination.

Although terrestrial carnivores such as raccoons, skunks, foxes and coyotes are known to harbor rabies in other parts of the country, bats are the only known reservoir for rabies in Washington state. Since 1989, only four non-bat animals have tested positive for rabies in Washington (two cats, a llama, and a horse), three of which were infected with a bat-variant of rabies (the strain type was unknown for the horse.)

If a person is exposed to rabies, infection can be prevented by administering rabies immune globulin and a series of rabies vaccine doses. To be effective, preventive treatment must be started before symptoms appear and must be given according to a specific schedule.

To identify persons potentially exposed to rabies and to ensure appropriate evaluation and preventive treatment if necessary
To ensure that potentially rabid animals are managed appropriately
To identify animal sources of rabies and risk factors for rabies transmission

Local epidemiology:

In 2015, 316 animal encounters were reported, 98 of which were determined to pose a risk for exposure to rabies and resulted in the recommendation for post-exposure preventive treatment. Seventy-five of the 98 suspected rabies exposures occurred within the United States. Bats accounted for all but one of the domestic exposures (the remaining was a bite by an unknown animal that occurred while hiking). In all instances, the bats were not available for rabies testing. The 23 animal encounters that happened while traveling internationally included contact with dogs (7), monkeys (7), bats (4), cats (4), and a lemur (1).

In Washington state, almost all cases of animal rabies occur in bats, however, most bats do not carry rabies. Five to ten percent of the sick or injured bats tested are positive for rabies each year. In 2015, 305 bats were tested for rabies in Washington; 9 (3%) were positive, none of whom were submitted for testing by King County.

The last identified cases of rabies in humans in Washington occurred in 1995 and 1997, both attributed to bat exposures. Prior to that, the last identified human case of rabies occurred in 1939 from the bite of a rabid dog. In 2011, reporting requirements were changed so that only animal bites that are suspected rabies exposures are immediately notifiable.